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We analyse exact solutions to the Riemann problem for a one-dimensional isentropic and perfectly conducting non-ideal dusty gas flow in the presence of a transverse magnetic field. We give the expression of wave curves as well as the behaviors of these wave curves. A new technique is provided to get a complete list of analytical solutions with the corresponding criteria. Moreover, the numerical solutions to the Riemann problem are also given. It is shown that the analytical solutions match well with the corresponding numerical solutions.

This paper is concerned with the analytical solutions to the Riemann problem for one-dimensional non-ideal dusty gas flow. We obtain explicitly the elementary wave curves to one-dimensional non-ideal dusty gas flow, and analyze the properties of these wave curves. On the basis of these preparations, by rigorously analyzing the uniqueness and existence of the solution to a system of two nonlinear equations, the analytical solutions are obtained. Besides, the corresponding numerical solutions are also provided. It is shown that the analytical solutions are identical with the corresponding numerical solutions.

In this paper, we study the exact solutions of Riemann problem for the compressible ideal fluid flow, where the external force is a continuous function of time. The exact expressions for contact discontinuity curve, shock wave curve and rarefaction wave curve are provided. Six types of exact solutions of the Riemann problem are also obtained. In particular, a vacuum arises at t > 0 although the initial data never involves the vacuum, and these solutions do not possess self-similarity in the ( t , x ) -plane.

The phenomena of concentration and cavitation and the formation of delta shock waves and vacuum states in vanishing pressure limits of solutions to the generalized Chaplygin Euler equations of compressible fluid flow are analyzed. It is proved that, as the pressure vanishes, any two-shock-wave Riemann solution of the generalized Chaplygin Euler equations of compressible fluid flow tends to a delta-shock solution to the transport equations, and the intermediate density between them tends to a weighted δ -measure that forms a delta shock wave; any two-rarefaction-wave solution is shown to tend to two contact discontinuities connecting the constant states and vacuum states, which form a vacuum solution of the transport equations. Moreover, some numerical simulations completely coinciding with the theoretical analysis are presented.

The Riemann problem for a perfect fluid model with zero pressure is considered, where the external force is a given continuous function of time. All of exact solutions are given. In particular, a vacuum occurs in the solutions, although initial data stay far away from the vacuum. It is shown that a delta shock wave in which density and internal energy contain a Dirac delta function develops in the solutions. The position, velocity, and weights of the delta shock wave are presented explicitly. Moreover, all of the solutions are not self-similar because of the presence of the external force.

In this paper, we consider limit behaviors of Riemann solutions to the isentropic Euler equations for a non-ideal gas (i.e. van der Waals gas) as the pressure vanishes. Firstly, the Riemann problem of the isentropic Euler equations for van der Waals gas is solved. Then it is proved that, as the pressure vanishes, any Riemann solution containing two shock waves to the isentropic Euler equation for van der Waals gas converges to the delta shock solution to the transport equations and any Riemann solution containing two rarefaction waves tends to the vacuum state solution to the transport equations. Finally, some numerical simulations completely coinciding with the theoretical analysis are demonstrated.

In this paper, we concern with the Riemann solutions to a compressible fluid described by the generalized Chaplygin gas, where the external force is a constant. Five exact solutions are given. In particular, the delta shock wave with a Dirac delta function in density and internal energy occurs in some solutions, and the location, velocity and weights of the delta shock wave are explicitly described. It is also noticed that because of the effect of the external force, these exact solutions are not self-similar.

We identify and analyze the phenomena of concentration and cavitation by studying the vanishing pressure limit of solutions to a simplified isentropic relativistic Euler equations. Firstly, both the explicit expressions and geometric properties of the rarefaction wave curve and shock wave curve based on any left state are given with the help of Lorentz invariance, and the Riemann problem for this system is considered. Then, we rigorously prove that, as pressure vanishes, any two-shock Riemann solution tends to a delta-shock solution of the pressureless relativistic Euler equations, and the intermediate density between the two shocks tends to a weighted $$\delta $$ -measure, which forms the delta shock wave. This describes the phenomenon of mass concentration. On the other hand, any two-rarefaction Riemann solution tends to a two-contact-discontinuity solution of the pressureless relativistic Euler equations and the nonvacuum intermediate state in between tends to a vacuum state, which reveals the phenomenon of cavitation. Both concentration and cavitation are fundamental and physical in fluid dynamics.

We concern with the Riemann problem the compressible fluid flow with the generalized Chaplygin gas. With the analysis on the phase plane, we rigorously confirm the occurrence of delta shock wave with Dirac delta function in density. Then the formation mechanism, generalized Rankine–Hugoniot relation and entropy condition for the delta shock wave are clarified. Based on these preparations, five kinds of exact solutions are obtained. Finally, the corresponding numerical results are also presented to illustrate our analysis.

We study the Riemann problem of the compressible Euler equations for the Chaplygin gas. With the analysis on the physically relevant region, we obtain two kinds of Riemann solutions by using the method of characteristic analysis. One composes of three contact discontinuities, and the other involves a delta shock wave in which both density and internal energy contain Dirac delta function simultaneously. We propose both generalized Rankine–Hugoniot relation and entropy condition for this type of delta shock wave. The numerical results coinciding with the theoretical analysis are also presented.

In this letter, we deal with a class of memristor-based neural networks with distributed leakage delays. By applying a new Lyapunov function method, we obtain some sufficient conditions that ensure the existence, uniqueness, and global exponential stability of almost periodic solutions of neural networks. We apply the results of this solution to prove the existence and stability of periodic solutions for this delayed neural network with periodic coefficients. We then provide an example to illustrate the effectiveness of the theoretical results. Our results are completely new and complement the previous studies Chen, Zeng, and Jiang ( 2014 ) and Jiang, Zeng, and Chen ( 2015 ).

We address the Riemann problem for the one-dimensional compressive flow of a van der Waals gas, in which the external force is a given continuous function of time. The explicit forms for shock wave, contact discontinuity and rarefaction wave are presented. The influence of van der Waals parameter on these elementary waves is discussed. Furthermore, we obtain six kinds of solutions to this Riemann problem and establish a condition for the occurrence of vacuum in the solutions. Particularly, all of the solutions are not self-similar in (t, x)-plane due to the presence of the time-dependent external force.

In this paper, an Nicholson's blowflies model with time-varying delays and a harvesting term is investigated. By applying the fixed point theorem, the properties of pseudo almost periodic function, inequality analysis technique and constructing appropriate Lyapunov functionals, we establish some new criteria for the existence and convergence dynamics of pseudo almost periodic solutions for the model. An illustrative example with its numerical simulation is presented to demonstrate the effectiveness of the derived results. Our results complement some previous studies.

This paper is concerned with interval general bidirectional associative memory (BAM) neural networks with proportional delays. Using appropriate nonlinear variable transformations, the interval general BAM neural networks with proportional delays can be equivalently transformed into the interval general BAM neural networks with constant delays. The sufficient condition for the existence and uniqueness of equilibrium point of the model is established by applying Brouwer's fixed point theorem. By constructing suitable delay differential inequalities, some sufficient conditions for the global exponential stability of the model are obtained. Two examples are given to illustrate the effectiveness of the obtained results. This paper ends with a brief conclusion. Copyright © 2016 John Wiley & Sons, Ltd.

In this study, we consider the two-dimensional Riemann problem for a system of conservation laws, which models polymer flooding in an anisotropic oil reservoir. The initial data are constants in three sectors centered at the origin, which only involve three contact discontinuities. By the generalized characteristic analysis method and the phase plane analysis method, we find that the solutions are not unique for certain values of the initial data. We propose an additional stability condition for the interaction of the contact discontinuities. By this stability condition, all of the exact solutions and their corresponding criteria can be obtained. The solutions exhibit various geometrical structures. In particular, envelope rarefaction waves develop in some solutions.

We propose a full Bayesian subset selection method for reproductive dispersion linear models, which bases on expanding the usual link function to a function that incorporates all possible subsets of predictors by adding indictors as parameters. The vector of indicator variables dictates which predictors to delete. An efficient MCMC procedure that combining Gibbs sampler and Metropolis-Hastings algorithm is presented to approximate the posterior distribution of the indicator variables. The promising subsets of predictors can be identified as those with higher posterior probability. Several numerical examples are used to illustrate the newly developed methodology.

We study the Riemann problem for the compressible Euler equations with the generalized Chaplygin gas. Based on the analysis on the physically relevant region, we obtain five kinds of exact solutions. It is shown that a delta shock wave with Dirac delta function in both density and internal energy develops in the exact solutions. The formation mechanism, generalized Rankine-Hugoniot relation and entropy condition are clarified for this type of delta shock wave. The numerical results are also presented to confirm this type of delta shock wave.

In this paper, we study the Riemann problem for a two-dimensional hyperbolic system of conservation laws with initial data projecting exactly three contact discontinuities. We use the generalized characteristic analysis method to analyze interactions of contact discontinuities, and obtain six analytical solutions and corresponding criteria. Delta shock waves and spiral structures appear in some solutions. We also conduct numerical experiments, and numerical results confirm the geometric structures of the constructed solutions.

This paper studies the two-dimensional Riemann problem for a hyperbolic system of conservation laws with three constant initial data separated by x -positive, y -positive and x -negative axes. Using the generalized characteristic analysis method, by considering the interactions of rarefaction waves, shock waves and contact discontinuities, 13 exact solutions and the corresponding criteria are obtained. Delta-shock waves appear in some solutions. Moreover, the numerical illustrations agree completely with the geometric structures of the exact solutions.

This paper is concerned with a class of neutral-type BAM neural networks with distributed leakage delays. By applying the exponential dichotomy of linear differential equations, Lyapunov functional method and contraction mapping principle, we establish some sufficient conditions which ensure the existence and exponential stability of almost periodic solutions for such BAM neural networks. An example is given to illustrate the effectiveness of the theoretical findings. The results obtained in this article are completely new and complement the previously known studies. Copyright © 2016 John Wiley & Sons, Ltd.

We study the global solutions to the two-dimensional Riemann problem for a system of conservation laws. The initial data are three constant states separated by three rays emanating from the origin. Under the assumption that each ray in the initial data outside of the origin projects exactly one planar contact discontinuity, this problem is classified into five cases. By the self-similar transformation, the reduced system changes type from being elliptic near the origin to being hyperbolic far away in self-similar plane. Then in hyperbolic region, applying the generalized characteristic analysis method, a Goursat problem is solved to describe the interactions of planar contact discontinuities. While, in elliptic region, a boundary value problem arises. It is proved that this boundary value problem admits a unique solution. Based on these preparations, five explicit solutions and their corresponding criteria can be obtained in self-similar plane.

In this paper, we investigate a class of stochastic shunting inhibitory cellular neural networks with time-varying delays. Applying integral inequality, some sufficient conditions on the existence and p-exponential stability of periodic solutions for stochastic shunting inhibitory cellular neural networks with time-varying delays are established. An example is presented to illustrate our main theoretical findings. Our results are new and complementary to previously known studies.